Central Air Conditioning
Buying Guide

Photo of two central air conditioning units outside a brick building.
Central Air Conditioning Buying Guide

The Coolness Quotient

If summertime temperatures leave you hot under the collar, you’re not alone. More than 75 percent of U.S. homes use air conditioning, and 90 percent of new homes are equipped with central air. And eco-conscious consumers will be gratified to know that today’s air conditioners are more energy efficient, which means they cost less to run while keeping you cool, calm, and comfy.

Installing or replacing central air can be a huge expense, so you’ll want to get it right. To ensure you have the best advice, we surveyed more than 16,000 Consumer Reports readers about new central air conditioning systems they bought and installed between 2008 and 2015. We learned how satisfied they were overall with their purchase, the cost of their most expensive repair, how many systems break, and which parts break most often.

1

Reader Reliability Results

For our reliability survey, we focused on two types of air conditioning systems: conventional, which are more common in areas with wide temperature swings, and heat-pump, which are typically used in areas with more moderate cooling and heating needs.

Heat pump systems, used for both cooling and heating, move warm air from your cool house outside when it’s hot and do the opposite during the heating season. Heat pumps are used for cooling about seven months a year while conventional systems are typically used five months a year.

2

Central Air Conditioning Types

The most common type of central air conditioning is the split system, which features a condenser outside the home, and a fan-and-coil system inside, connected by pipes carrying refrigerant. However, not every home can accommodate the ductwork needed to install central air, and a split ductless system is an option.
 

Photo of a central air conditioning unit.

Central Air Conditioning

Central air-conditioning systems use ducts to distribute cooled air throughout the house. In a "split system," the most common design, refrigerant circulates between an indoor coil and a matching outdoor condenser with compressor. The refrigerant cools the air, dehumidifying it in the process; a blower circulates air through ducts throughout the house. A variation is the "heat pump," a type of system that functions as heater and cooler.  

Photo of a heat pump central air conditioning unit.

Heat Pump Air Conditioners

Heat pump air conditioners are common in regions with moderate heating and cooling needs. During the cooling season, heat pumps move warm air from your cool house outside. During the heating season, they do they opposite. Systems with heat pumps are typically in use for cooling for a median of seven months a year.  

Photo of a split ductless air conditioning system.

Split Ductless Systems

Split ductless systems have an outside condenser and one to four indoor blower units mounted high on the wall. Tubing connects these parts and circulates refrigerant. The tubing, along with an electric and drain line, is run through about a 3-inch hole hidden behind each indoor unit. Each indoor unit cools the room in which it's installed and has its own remote control. Split ductless systems need no ductwork, making them easier to add to homes without existing ducts. They can be more expensive than window air conditioners, and professional installation is recommended.

3

How an Air Conditioner Works

To provide cooling throughout the home, air conditioners transfer heat from a home's interior to the outside.

Illustration of how central air conditioning works.
Illustration: Chris Philpot
4

Keep Your Ducts in a Row

If you are installing an A/C system from scratch, your contractor should calculate the size of the cooling equipment you need by using such recognized methods as the Air Conditioning Contractors of America (ACCA) Manual J. If you already have ductwork for your heating, adding a central system can cost less.

Keep in mind that ducts used for heating might not be the right size or in the right location for optimal cooling. Your contractor should ensure duct sections are properly sized and that there are enough supply registers to deliver sufficient air to the right spots. Undersized ductwork can make for inefficient and noisy operation. Maintenance tips for keeping your AC running smoothly:

Keep it clean. Be sure hedges and plants are at least 2 feet away from the outside unit. Clean grills and filters monthly. Clear debris and dirt from condenser coils and check for blockages in the drainpipe.

Seal and insulate ducts. Cool or warm air can escape through leaks or when ducts aren't insulated properly, wasting up to 40 percent of the energy used to run your system. Sealing your ducts will keep you cooler in the summer and warmer in the winter. That’s why it’s called duct tape, not duck tape.

Seasonal checks. Once a year have a licensed professional change all filters, clean and flush the coils, drain the pan and drainage system, and vacuum the blower compartments. The contractor should also check that the system is properly charged with refrigerant, that there are no leaks, and that all mechanical components are working properly.

5

Important Factors In Choosing Central AC

Size
A synonym for the air conditioner's cooling capacity, size is measured in British thermal units per hour (Btu/hr.) or in "tons." One ton of cooling equals 12,000 Btu/hr. For sizing guidance, use the calculator on the Energy Star website.

Efficiency
This describes how much cooling the unit delivers for each watt of electricity. Efficiency is expressed as the Seasonal Energy Efficiency Rating, or SEER. The minimum SEER for a split system central air conditioner allowed today is 13, so look for units with SEER ratings of 13 or greater. The higher the SEER, the more you can lower your energy costs.

Maintenance
A service plan that combines regular inspections with discounts on repairs and a labor warranty is worth negotiating into the overall price. Prices for such a service vary widely.

Programmable thermostats
Proper use of a programmable thermostat can reduce your cooling costs by up to 20 percent. And using a box or ceiling fan, which cost little to run, can make you feel 3 to 4 degrees F cooler.

Upgrading an existing system
If you're upgrading your central air, don't assume you should buy the same-sized system. Any changes you've made to improve your home's energy efficiency, such as upgrading your windows or adding insulation, can reduce your cooling needs. On the other hand, if you've added rooms, you might need more cooling.

Have your contractor do a load calculation based on a recognized method, such as Manual J from the ACCA. The contractor's evaluation should include whether your ducts need to be resized, sealed and insulated, or replaced. Remember that an indoor evaporator coil and outdoor condenser must be a matched set from the same brand, or else the performance, efficiency, and capacity may not meet expectations.

New systems are 20 to 40 percent more efficient than minimum-efficiency models made even 10 years ago. Costs will vary and can depend on whether you need ductwork installed and the particular size and configuration of your home.

6

Installation: Find the Right Contractor

Whether you're replacing an older air conditioner or installing one for the first time, finding a trustworthy contractor to install and service an air-conditioning system matters the most. Here's what to do.

Ask around. Seek referrals from neighbors, family, or business associates. It's wise to get price quotes from at least three contractors.

Check their background. Contractors who bid on your installation should show you verification of bonding and insurance, plus any required contractor's licenses. Check with your local Better Business Bureau and consumer affairs office for complaint records. It's a plus if technicians are certified by a trade organization, such as North American Technician Excellence or HVAC Excellence, to service residential heating and cooling equipment. Those and other similar programs assess the technician's knowledge of specific types of equipment and their proper service methods.

Get specifics. Contractors who bid on your job should calculate required cooling capacity by using a recognized method such as the ACCA's Residential Load Calculation Manual, also called Manual J. An additional reference for assessing ductwork needs is Manual D. The calculations produce a detailed, room-by-room analysis of cooling needs. Ask for a printout of all calculations and assumptions, including ductwork design. Be leery of a contractor who bases estimates merely on house size or vague rules of thumb.